This invention relates to a conveyor tube for use in installing or replacing a well tool in a producing well. More specifically it is a conveyor tube which runs along the outside of the production tube of the producing well, wherein the conveyor tube is designed to be able to move well tools, which may be for example, but are not limited to, sensors for sensing well parameters and/or flow directors for guiding circulation in sections of the production tube, to a predetermined position. The invention also relates to procedures for using it.
The object of the invention is to provide a device and method for installing and replacing well tools in a producing well without the need for complicated and demanding well completion work.
In the petroleum industry it is desirable, for economic reasons among others, to maintain production to the maximum possible degree.
It is also necessary to conduct measurements of parameters in the well that are important for controlling production, calculating the present reservoir fluid, drainage efficiency and so on. To sense the desired parameters it is now normal practice to install sensors permanently in wells. The sensors communicate through cables laid through the valve tree of the well to a surface installation from which the well is monitored and controlled.
The well environment has been shown to have a degrading effect on the sensors used due, among other things, to the harsh environment that frequently prevails in a well. The failure of sensors after being installed in wells is therefore felt to be a problem. In order to replace a sensor that has failed the entire well completion must be pulled to the surface to provide access to the sensor. When this takes place the well must be protected against leakage, and barriers must be fitted against the reservoir. Such barriers result in stoppage of production whilst the replacement operation is being carried, resulting in economic loss.
To reduce some of the disadvantages of the above-mentioned method of prior art attempts have been made to develop procedures for carrying out an intervention in a well to replace a damaged measuring instrument that has been installed in a so-called side pocket (“side pocket mandrel”). In this case a tool is inserted which pulls out the measuring instrument installed in a pocket in the production tube. A new intervention (operation) is then carried out to insert a new measuring instrument. This is done by means of a cable (“wireline”) or coiled tubing.
One major drawback of this procedure is that an expensive electrical or fibre optic coupling must be used which is connected in the “wet” condition in the well fluid. This coupling has proved to be unreliable and the procedure is therefore little used in the petroleum industry.
In the petroleum industry it is also necessary to pump different types of auxiliary tools into the well production tube. After this, the pumped-in auxiliary tool must be circulated until it reaches the desired position in the well. In this specialist field this is called TFL (“Through Flow Line”) or Pump Down Tools, and it is based on running an insert line parallel with the production tube, and has the same diameter as it. The two tubes mentioned are connected at a circulation point in the well, the circulation point being installed as far down in the well as possible, normally just above the production packing. A major disadvantage of the TFL technology of prior art is that the possibility of circulation is lost if the production tube is blocked above the circulation point.
American patent U.S. Pat. No. 4,940,094 shows a procedure and a device for operating a circulating valve down in a well using TFL technology, as described above, wherein production takes place through the insert line through which the device is fed to operate the aforementioned circulating valve.
The object of the invention is to obviate or at least reduce one or more disadvantages of the method of prior art.